This invention relates to aerosol dispensers for fluid products, comprising a piston pump assembly for generating in the interior of the dispenser compressed air serving as propellant, and improved product flow control means. Various types of aerosol dispensers utilizing compressed air for dispensing fluids in the form of a spray are known. Among them are especially aerosol dispensers for liquid products described in U.S. Pat. No. 3,369,757 granted on Feb. 20, 1968 to M. Boris, which dispensers comprise a container for product to be dispensed, a piston pump separately from the product container, for generating compressed air as a propellant, a spray nozzle in which compressed air flowing therethrough aspirates, and sprays, product from the product container, flowpaths for compressed air and product to the spray nozzle from, respectively, the piston pump and the product container, and obturating means associated with the said flowpaths and opening these paths in dependence on a determined compression position of the piston in the cylinder of the aforesaid piston pump.
These known dispensers suffer from the drawback that the timely opening of the obturating means for the compressed-air flow which comprise a spring-biassed ball valve, is effected by the pressure of the compressed air alone, and hence not reliable as it depends on the quality and age of the spring material, and the valve must open before a valve shaft controlling the product flowpath can open. This leads unavoidably to a loss of compression.
In order to overcome this drawback, there is described in Belgian Pat. No. 768,039, granted on December 3, 1971 to the Applicant, an improved type of the above-described aerosol dispensers, wherein at least the valve controlling the flow of compressed air is opened by the mechanical action of rigid force-transmitting means comprising abutment means on the piston of the piston pump and on a displaceable valve disk or stem or the like valve body pertaining to the compressed air flow-controlling valve, which abutment means on the piston and valve body act one upon the other by direct contact or on lever means acting on the aforesaid valve body.
In a further development of this improved type of aerosol dispenser, the product container is replaceably mounted on top of a valve housing for the obturating means for the control of both flowpaths mentioned above, and which valve housing has a dependent sleeve forming the cylinder of the aforesaid piston pump, while the piston bears a mantle-type sleeve portion surrounding the cylinder-and-valve housing assembly as an outer guiding and protecting means.
However, with certain fluid products to be dispensed it may easily occur that deposits of aged or decomposed residual product are formed in the product flowpath leading through the valve housing to the spray nozzle, and especially in the later.
When this happens the entire dispenser has to be thrown away.
As the springs, which are usually made of steel, and the piston pump assembly constitute the more expensive part of such dispensers, U.S. Pat. No. 3,764.046 describes an aerosol-dispenser of the above-described type, wherein the product container and the spray nozzle insert are part of a replaceable unit, while the piston pump assembly including a compressed air flow-controlling valve means and springs is retained by the user, so that the above unit, which can be mass-produced and is hence inexpensive, is replaced each time a full product container is substituted for an empty container.